crush/CrushTester: check for overlapped rules

crush/CrushTester: check for overlapped rules

list rules if there are more than one of them can be chosen by the CRUSH
for a given ruleset, pool type and a pool size. this is not entirely a
buggy crush map, but it might be worthy to get the attention of the user
that multiple rules overlap with each other, and only the first one will
be used by the CRUSH.

Signed-off-by: Kefu Chai <kchai@redhat.com>